Transmission window for particle accelerator

ABSTRACT

A particle accelerator has a transmission window formed of a thin homogeneous foil having a predetermined thickness and having a predetermined length, and when laid fiat as a sheet having a transverse dimension. The window is formed to have a locus of a curve in cross section along the transverse dimension such that a radius of curvature of at least a portion of the curve in cross section is less than the length of the transverse dimension. Longitudinal channel and tubular shapes are preferred. Window cooling by gaseous and liquid fluid flows is also described. A transmission window assembly and a particle beam accelerator having an efficient rugged accelerator tube structure are also described. As one example, a liquid material processor and processing method employs either the curved window or a conventional window and advantageously directs liquid material onto the window to cool it, while a particle beam passing through the window enters the liquid material and changes it chemically in a predetermined manner. A mobile transporter enabling relocation of the liquid material processor between process sites is also described.

REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 07/748,987, filed on Aug. 16, 1991, entitled"Transmission Window for Particle Accelerator", now abandoned, which isa continuation-in-part of U.S. patent application Ser. No. 07/569,092filed on Aug. 17, 1990, entitled "Transmission Window for ParticleAccelerator", now abandoned. The present application is also related toa commonly assigned, copending U.S. patent application Ser. No.07/569,329, also filed on Aug. 17, 1990, and entitled "Particle BeamGenerator", now U.S. Pat. No. 5,051,600, the disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to improvements in high energy particleaccelerators especially for use within industrial processes for treatingvarious materials. More particularly, the present invention relates toan improved transmission window for a particle accelerator and improvedcooling methods and apparatus for drawing heat away from thetransmission window, and for simultaneously processing the coolant.

BACKGROUND OF THE INVENTION

Particle accelerators are employed to irradiate a wide variety ofmaterials for several purposes. One purpose is to facilitate or aidmolecular crosslinking or polymerization of plastic and/or resinmaterials. Other uses include sterilization of foodstuffs and medicalsupplies and sewage, and the destruction of toxic or polluting organicmaterials from water, sediments and soil.

A particle beam accelerator typically includes (i) an emitter foremitting the particle beam, (ii) an accelerator for shaping the emittedparticles into a beam and for directing and accelerating the highlyenergized particle beam toward a transmission window, (iii) usually abeam scanning or deflection means and (iv) a transmission window andwindow mounting. A generator is provided for generating the considerablevoltage difference needed to power the accelerator.

The emitter and the accelerator section, which may comprise centrallyarranged dynode elements or other beam shaping means, or electrostaticor electromagnetic lenses for shaping, focusing and directing the beam,are included within a highly evacuated vacuum chamber from which airmolecules have been removed so that they cannot interfere with theparticle beam during the emitting, shaping, directing and acceleratingprocesses.

The term "particle accelerator" includes accelerators for chargedparticles including, for example, electrons and heavier atomicparticles, such as mesons or protons or other ions. These particles maybe neutralized subsequent to acceleration, usually prior to exiting thevacuum chamber.

The transmission window is provided at a target end of the vacuumchamber and enables the beam to pass therethrough and thereby exit thevacuum chamber. The workpiece to be irradiated by the particle beam isusually positioned outside the accelerator vacuum chamber and adjacentto the transmission window in the path of the particle beam.

As used herein, "transmission window" is a sheet of material which issubstantially transparent to the particle beam impinging thereon andpassing therethrough. The transmission window is mounted on a windowmounting comprising a support frame which includes securing andretention means which define a window envelope.

The conventional beam transmission window, usually rectangular withfilleted corners and generally perpendicular with respect to alongitudinal axis of the particle beam, must be sufficiently thin and ofa suitable material so as not to attenuate the beam unduly from energyabsorption and consequent heating. The window material must besufficiently strong to withstand the combined stresses due to thepressure difference from typical ambient atmospheric pressure on oneside thereof and high vacuum on the other and due to the heat generatedby the particle beam in passing therethrough.

Conventionally, transmission window foils have typically been loinstalled between rectangular, generally flat flanges with filletedcorners. The thin window foils are typically formed of titanium ortitanium alloy sheets or foils which typically range in thicknessbetween about 0.0005 inches (0.013 mm) and 0.004 inches (0.104 mm). Muchthicker stainless steel foils have been employed as transmission windowsin irradiation apparatus for waste water/effluent processing.

When vacuum is drawn on one side of a conventionally installed, flatfoil window, the ambient air pressure on the other side tends to deformor "pillow" the foil window slightly. Part of this deformation resultsfrom transverse stretching of the foil. The radius of curvature of thefoil resulting from drawing a vacuum is defined by the amount oftransverse stress incurred. The relation therebetween for a foil ofindefinite length (that is, neglecting end effects) is given by thefollowing:

    S1=(p(R/t) transverse stress (lb/in2)

where

p=differential pressure across foil (lb/in2)

R=radius of curvature (inches)

t=thickness of foil (inches); and

S2=S1² axial stress (lbs/in2)

and the total stress S at any position on the window is given by:

    S=(S1.sup.2 +S2.sup.2) (given in lbs/in2).

Because the window is not of indefinite length, the ends thereof aresubjected to additional axial stress as well as transverse stressbecause of the transverse and end retention structure adjacent thereto.The combination of axial and transverse stresses often results inwrinkling, non-uniform deformation, or even actual creasing at thewindow ends, and increases the chances of premature failure thereat.

Because the sheet or foil materials used for conventional windowconfigurations have inherent strength limitations, particle acceleratorpower output is limited, not by the high voltage generator capacity, butby the maximum heating due to the particle flux that the window materialcan withstand. The prior art has therefore sought to minimize theincrease in temperature of the window during accelerator operation ordecrease the mechanical stress it is subjected to. One known techniqueincludes, for example, providing support grids inside the acceleratorchamber and abutting against the window. In this particular technique,the support grids are often cooled by coolant flowing through internalcooling passages. While this technique effectively increases the activewindow area, the grids used in these known designs are within the beampath and therefore undesirably absorb a significant fraction of theincident accelerated particles. By "active window area" is meant thatarea of the window within and defined by the securing structure andhaving an active transverse dimension. A related technique of increasingthe window area without providing additional support increases thetendency of the window foil to fail under stress. Thus, a hithertounsatisfied need has arisen for an improved transmission window designwherein a given thickness of window foil can withstand a much higherparticle flux than that contemplated heretofore.

The efficacy of radiation-thermal cracking (RTC) and viscosity reductionof light and heavy petroleum stock, for example, has been reported inthe prior art. Also, high energy particle experiments have beenconducted in connection with processing of aqueous material includingpotable water, effluents and waste products in order to reducechemically or eliminate toxic organic materials, such as PCBs, dioxins,phenols, benzenes, trichloroethylene, tetrachloroethylene, aromaticcompounds, etc.

The techniques heretofore employed have typically presented a liquidsheet or "waterfall" in front of, but spaced away from, the particlebeam. Conventional wisdom associated with these techniques has been toemploy very highly energetic particle beam sources (e.g. 1-3 MeV) inorder to obtain sufficient particle penetration. In order to processusefully large quantities, high beam currents, such as 50 milliamperesor more have also been proposed. High energy and high beam currentsrequire very expensive voltage generation and beam forming apparatus.

However, McKeown (Radiation Physics and Chemistry, volume 22, 1983, pp419-430) in a paper entitled "Electron accelerators--a new approach" hasdisclosed a waste water irradiation target chamber comprising a curvedvacuum window of 0.75 mm thick stainless steel welded to a fiat windowsurround, apparently of the same material. Waste water to be irradiatedpasses through a u-shaped structure containing the window in one arm.The impinging scanned electron beam was produced by a microwaveaccelerator and had an energy of 4 MeV. He states: "The scanned 4 MeVbeam penetrated a 0.75 mm thick stainless steel into a fast flowingeffluent target to test the design criteria of the mechanical andthermal stresses in the window . . . Experiments showed that sustainedpower dissipation of 100 W/cm² on the window showed no deterioration andfailure occurred at 3.5 times this design value."

A power dissipation of 100 W/cm² in a window 0.75 mm thick results in athermal load to the scanned portion of the window of 168 W/g (watts pergram). Failure thus occurred at a window thermal loading of 584 W/g.Energy losses in a 4 MeV beam passing through such a window would exceed24%, that is, about 33.8 keV per mil of window thickness. Furthermore,on page 423 of this reference it is stated "FIG. 6 is a symbolicrepresentation of the main elements which make up a linac-basedaccelerator. The efficiencies shown have already been achieved underoptimum conditions and it now seems possible that total conversion ofmain power to electron beam power in the target could exceed 50%." FIG.6 of this reference shows that the conversion efficiency before thewindow for a 10 MeV linac is 60.6%. As the window shown in this figureis stated to pass electrons of this energy through with 90% efficiency,the total delivered efficiency would be expected to be 54.53%.

The use of a thin sheet of liquid material being irradiated has not beensimultaneously employed to transfer heat away from a curved transmissionwindow of the beam. Heretofore, there has been an unsolved need for alower particle energy, higher beam current, higher efficiencyirradiation apparatus for radiation processing of materials such aspetroleum stock, potable water, effluents and other aqueous and liquidmaterials. We have discovered that, contrary to the teachings of McKeownand the general understanding of the prior art, by the use of a curvedtransmission window one can greatly reduce the stresses caused by thepressure differential thereacross during operation, thereby enabling useof highly electron transparent window foils in demanding operatingconditions. This discovery enables us to provide a highly efficientrugged high power particle accelerator apparatus, which may easily berendered transportable.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a novel transmissionwindow design whereby the window foil is subjected to lower transversestress, lower axial stress and lower total stress when subjected to apressure difference between the two faces thereof, which is more readilyand effectively cooled, and which still enables substantially all, e.g.at least 80%, preferably 90% or even at least 95%, of the acceleratedincident particles to pass therethrough in a manner which overcomes thelimitations and drawbacks of the prior art.

A further object of the invention is to provide a compact transportablerugged high power, high efficiency particle accelerator apparatus forthe radiation processing of the materials carried in fluid mediums whileat the same time advantageously using the fluid medium for the efficientcooling and conducting of heat away from a transmission window of theparticle accelerator.

One more object of the present invention is to provide an improvedtransmission window configuration for a particle accelerator in whichoverall stress for a given particle flux is considerably reduced overthat manifested using a substantially flat window of equivalent activearea.

The term "overall stress" means the combined stress due to the pressuredifference across the window between atmospheric pressure on one sidethereof and high vacuum on the other as well as due to the increase intemperature caused by the energy given up by a given particle flux intraversing the window which temperature increase results in a decreasein the ability of the window material to resist mechanical stress. By"substantially flat" we mean that the window in the absence of anypressure difference thereacross has a radius of curvature which isrelatively large, for example, 100 times the active transverse dimensionthereof. Thus, the radius of curvature of such flat windows isessentially infinite in the absence of any curvature resulting from theapplication of a pressure differential across the thickness thereof whenthe window is first mounted in the accelerator. Of course, once a vacuumis drawn on one side of the window when mounted in the acceleratorhousing, the nominally fiat window will tend to yield both elasticallyand to some degree permanently. For titanium windows the deformation islargely elastic, and these foils substantially recover from suchdeformation when the deforming stress is removed. Aluminum windows usedin the prior art often undergo some amount of permanent deformationafter initial application of a pressure difference thereacross andexhibit some degree of "dishing" thereafter.

Another object of the present invention is to provide a transmissionwindow which reduces transverse stress by providing an active areafollowing a curved contour in transverse cross-section such that aradius of curvature thereof is less than twice the length of the activetransverse dimension.

Yet another object of the present invention is to provide methods andapparatus for the radiation processing of materials carried in fluidmediums while at the same time advantageously using the fluid medium forthe efficient cooling and conducting of heat away from a transmissionwindow of a high power, low energy, preferably ruggedized andtransportable particle accelerator. This method of using the processmaterials and fluid medium for cooling the window also achieves thedesired result of raising the temperature of the materials in acontrolled fashion as may be conducive to desired chemical reactions. Byplacing the materials to be processed into direct,proximity of the beamwindow for cooling it also advantageously increases the incidence ofenergetic particles and electrons in the material, leading to a desiredprocess result at lower beam energies, and therefore lower cost andcomplexity, than heretofore achieved.

A further object of the present invention is to provide a transmissionwindow which may be cooled more efficiently with a cooling fluid stream,thereby increasing the capacity of the window to dissipate higher powerlevels for a given window foil thickness.

Yet another object of the present invention is to provide an improvedand more efficient cooling arrangement and method for conducting heataway from a transmission window of a high energy particle accelerator,thereby increasing the capacity of the window to dissipate higher powerlevels for a given window foil thickness.

In accordance with principles of the present invention a transmissionwindow for a particle accelerator is formed from a thin homogeneous foilhaving a predetermined thickness and having a predetermined lengthbetween a first end and a second end, and a width, when laid fiat as asheet prior to forming. The window along at least part of its lengthcomprising an active area is formed to have the locus of a curve incross section along an active transverse dimension such that a radius ofcurvature R of at least a portion of the curve in cross section is lessthan twice the length of the active transverse dimension.

In one presently preferred specific embodiment of the present invention,a particle beam accelerator includes a housing defining a vacuumchamber, a charged particle source for generating a particle beam withinthe vacuum chamber and a particle accelerator for accelerating anddirecting the particle beam toward a first end of the housing which hasbeen adapted to allow accelerated particles to pass therethrough. Thehousing includes an upper flange at the first end and a removable lowerflange which mounts against the upper flange. The terms "upper flange"and "lower flange" as used in this specification are to be understoodand interpreted in relation to the particle beam direction, the upperflange being closer to the particle source than the lower flange. Theupper flange and the lower flange together include a securing mechanismto secure the homogeneous window foil which is mounted therebetween anddefines aligned openings to the interior of the chamber which have alength and an active transverse dimension. The aligned openings may ormay not be coextensive. The upper flange and the lower flange furtherdefine a curved locus at each of said first and second ends along theactive transverse dimension. A transmission window is formed ofhomogeneous foil sheet material of a size sufficient to cover thealigned interior openings of the upper and lower flanges and thesecuring mechanism, and being of predetermined thickness. Thetransmission window is removably mountable between the upper flange andthe lower flange such that the curved locus at each end along the activetransverse dimension forms the homogeneous transmission window into acurved channel configuration having a finite radius of curvature incross section along at least a portion of the transverse direction, theportion preferably being substantially the whole length of the activetransverse dimension, but not greater. The term homogeneous foil orhomogeneous (transmission) window when used in this specification meansthat the foils or window is substantially uniform in composition andstructure, that is, without welds, bonds, seams or joints. A singlelongitudinal seamline to form the foil window as a tube is within ourcontemplation of "homogeneous" as used herein.

In one aspect of the above described embodiment, the particle beamaccelerator further comprises a sealing gasket disposed between thetransmission window and the upper flange and functioning as a sealingmechanism therefor.

In another presently preferred embodiment of the present invention, thecurved transmission window may be formed to define a cylindrical tubethrough which a strand is drawn for radiation processing by the particlebeam.

In another aspect of the invention the active area of the transmissionwindow prior to being mounted between the upper and the lower flanges ofthe accelerator housing is not substantially planar. Preferably, thetransmission window of this aspect of the invention is preshaped topresent a convex surface of generally elliptical shape to the vacuumchamber.

In yet another aspect this invention provides a particle beamaccelerator including a housing defining a vacuum chamber. A particlebeam generator for generating a particle beam is within the vacuumchamber, as is a beam focussing and directing structure for directingthe particle beam toward a radiation emission end of the housing. Thehousing includes an upper flange at the emission end and a removablelower flange. The upper flange and the lower flange define alignedinterior openings. The openings have a length and an active transversedimension. A transmission window is formed from a fiat foil sheetmaterial of sufficient length and width so that after formation thewindow covers the aligned interior openings of the upper and lowerflanges and window mounting mechanism. The window is of a predeterminedthickness. The transmission window is removably mountable between theupper flange and the lower flange, such that the active area of thetransmission window is at least 0.6 square inches, and such that thewindow is capable of withstanding energy deposition from the beam of atleast 50 watts per square inch for a period of at least 1 hour withoutmechanical failure. Preferably, the window has an active area of aminimum of at least 1 square inch, for example 5 square inches, and mostpreferably an active area of 10 square inches; and it can withstand anenergy flux from the beam of at least a minimum of about 75 watts persquare inch, for example 100 watts per square inch, especially 125 wattsper square inch, and most preferably at least 150 watts per square inch.

As still a further facet of the present invention, a liquid materialprocessor includes a housing containing a particle beam acceleratordefining a vacuum chamber, a particle beam generator for generating aparticle beam within the vacuum chamber, a particle beam focusing anddirecting structure for directing the particle beam toward a radiationemission end of the vacuum chamber, the housing including a transmissionwindow at the radiation emission end for passing the particle beam andbeing formed of thin foil sheet material. In this facet of theinvention, the processor comprises a source for supplying a quantity ofliquid material to the housing, a liquid material flow directingstructure within the housing and external to the vacuum chamber fordirecting a flow of liquid material supplied from the source: against anexterior surface of the transmission window in order to transfer heatfrom the transmission window to the liquid cooling fluid whilesimultaneous exposure to the particle beam modifies chemically theliquid cooling fluid, thereby resulting in processing of the liquidcooling fluid into processed liquid, and a liquid collection vesselwithin the housing for collecting the processed liquid.

As one aspect of this facet of the invention, the liquid collectionvessel defines a gaseous cavity above a liquid level, and the processorfurther comprising a pump, such as a vacuum pump, in communication withthe gaseous cavity for reducing gas pressure within the cavity.

As another aspect of this facet of the invention, a heat exchanger isprovided for exchanging heat from the processed liquid within the liquidcollection vessel to the supply of liquid material within the source.

As a further aspect of this facet of the invention, the housing includesplural flanges, each flange defining a curve locus in an activetransverse dimension lying in a plane substantially perpendicular to alongitudinal dimension. The transmission window is of a size sufficientfollowing formation to enclose the curve locus of the plural flanges andextends therebetween in the longitudinal dimension and is of apredetermined thickness. Further, the transmission window is removablymountable between and positioned by the plural flanges such that thecurve locus followed by the transmission window has a radius ofcurvature which does not exceed twice the length of the activetransverse dimension.

As a related aspect, the liquid material directing structure causes theflow of liquid material to be directed in accordance with an activetransverse dimension of the transmission window. As a further relatedaspect, the liquid material directing structure comprises a knife-bladeedge positioned adjacent to an edge of the active transverse dimension.In one more related aspect, the knife-blade edge is adjustablypositionable in order to control thickness of a liquid sheet of theliquid cooling fluid as applied to cool the transmission window whileundergoing the chemical processing.

In accordance with a further facet of the present invention, a method isprovided for processing materials by exposure to an accelerated particlebeam. The method essentially comprises the steps of:

generating a particle beam within a vacuum chamber,

directing the particle beam toward a particle beam transmission windowat a radiation emission end of the vacuum chamber,

supplying from a source a quantity of said material to be processedwithin a fluid medium, such as a liquid,

directing a flow of the fluid medium supplied from the source against anexterior surface of the particle beam transmission window in order totransfer heat therefrom to the medium,

simultaneously exposing the material in the fluid medium to acceleratedparticles of said particle beam passing through the transmission windowmeans in order to process the material.

As one aspect of this facet of the invention, the step of exposing thematerial to accelerated particles of the particle beam causes chemicalmodification of the material.

As another aspect of this facet of the invention, a further step isprovided for collecting the fluid medium and processed material afterheat transfer to the medium and simultaneous exposure of the material tothe accelerated particles.

As one more aspect of this facet of the invention, the medium itselfcomprises the material to be processed.

As yet another aspect of this facet of the invention, further stepsinclude: providing an enclosed processing chamber including the exteriorsurface of the particle beam-transmission window, and reducing gaspressure within the enclosed processing chamber to relieve stresses inthe particle beam transmission window.

As a still further aspect of this facet of the invention, a further stepof exchanging heat from the fluid medium to an external heat transfermedium is carried out.

Yet another aspect of this facet of the invention includes the furtherstep of forming the particle beam transmission window means as a curvedstructure so that said external surface thereof has an active area alongat least part of its length so that a locus of a curve in cross sectionalong an active transverse dimension of the active area has a radius ofcurvature R of at least a portion of the curve in cross section lessthan twice the length of the formation transverse dimension.

Still one more aspect of this facet of the invention includes the stepof forming the particle beam transmission window means as a curvedstructure to follow guiding surfaces of plural flanges, each flangehaving a guiding surface defining a curve locus in an active transversedimension lying in a plane substantially perpendicular to a longitudinaldimension, the particle beam transmission window being of a sizesufficient following formation to enclose the curve locus of the pluralflanges and extending therebetween in the said longitudinal dimensionand being of predetermined thickness.

As still one more aspect of this facet of the invention, the step ofdirecting the flow of fluid medium includes the step of directing theflow of fluid medium to be directed in accordance with an activetransverse dimension of the particle beam transmission window. As arelated aspect, this step includes forming and directing a the fluidmedium as a thin sheet of liquid against the particle beam transmissionwindow along a longitudinal edge thereof.

As one more aspect of this facet of the invention, further steps ofcollecting the fluid medium following heat transfer from the particlebeam transmission window; and, transferring heat from the collectedmedium to said quantity of the material to be processed within themedium before it is directed against the particle beam transmissionwindow, are carried out.

These and other objects, advantages, aspects and features of the presentinvention will be more fully understood and appreciated uponconsideration of the following detailed description of a preferredembodiment, presented in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Drawings:

FIG. 1 is an exploded isometric view of a transmission window for aparticle accelerator which incorporates the principles of the presentinvention.

FIG. 2 illustrates a transmission window of the invention which iscontoured at each end by a preform in order to present a curved convexsurface to the vacuum chamber and facilitates ready installation.

FIG. 3 illustrates a transmission window of the invention which has beenpreshaped to present a convex surface to the vacuum chamber and whichcan be mounted between substantially fiat surfaces of the upper andlower window mounting flanges.

FIG. 4 is a somewhat diagrammatic view in transverse cross section andelevation of the FIG. 1 particle accelerator transmission window mountedbetween an upper flange and a lower flange, showing curved edges of theupper flange around which the transmission window is formed andsupported, showing a nozzle for creating a sheet of cooling fluiddirected to pass adjacently against the curved transmission window,showing a beam absorption structure below a strand or tubular workpiece,and showing a deflected and converged particle beam for radiationprocessing of the strand or tubular workpiece.

FIG. 4A is a view similar to FIG. 4, except that the FIG. 1 acceleratedparticle beam is deflected and not converged, and the workpiececomprises a continuously moving sheet passing below the beam.

FIG. 5 is a somewhat diagrammatic view in cross section and elevation ofan alternative preferred embodiment, illustrating a fluid coolingarrangement for conducting heat away from the transmission window andfor promoting centering of the workpiece in the particle beam passingthrough the transmission window.

FIG. 6 is a diagrammatic isometric view of an embodiment of the presentinvention including an upper flange and transmission window, and of alower flange mounted to the upper flange, wherein the lower flange isprovided with passageways enabling gaseous cooling fluid and coolingliquid to flow, thereby to conduct heat away from the transmissionwindow and the vicinity of the strand being treated with particle beamradiation.

FIG. 7 is a view in side elevation and cross section of the FIG. 6embodiment along the section line 7--7 in FIG. 6.

FIG. 8 is a diagrammatic isometric view of a tubular particle beamwindow structure also embodying the principles of the present inventionmounted between two mounting flanges of an evacuated chamber of aparticle beam accelerator.

FIG. 9 is a view of the FIG. 8 tubular window mounted between twomounting flanges of an evacuated chamber of a particle beam accelerator.

FIG. 10 is an enlarged, somewhat diagrammatic view in side elevation ofmodified structure for mounting the FIG. 8 tubular transmission windowand for directing a substantially cylindrically layered cooling fluidflow at the inside/ambient environment surface of the FIG. 8 tubularwindow and for creating an axially centralized low pressure region inthe window for promoting centering of the product strand to be treatedby particle beam bombardment.

FIG. 11 is a diagrammatic side view in section and elevation of a liquidmaterials processing beam which employs the liquid material beingirradiated also to cool the transmission window in accordance withprinciples of the present invention.

FIG. 12 is a slightly enlarged, even more diagrammatic side view insection and elevation of the FIG. 11 liquid materials processingparticle beam.

FIG. 13 is a diagrammatic side view in section and elevation of aparticle beam petrochemical processing system, also incorporating theprinciples of the present invention.

FIG. 14 is a diagrammatic side view in section and elevation of atransportable environmental liquid processing system embodyingprinciples of the present invention.

FIG. 15 is a graph of particle beam power for a given area beamtransmission window and a family of process radiation dosages as afunction of process fluids flow, wherein the process fluid removes heatfrom the transmission window in accordance with the present invention.

FIG. 16 is a somewhat diagrammatic view in elevation of the structure ofa preferred beam focussing and directing tube section, showing it inrelation to an electron gun assembly.

FIG. 17a is a magnified view of a portion of FIG. 16 showing structuralfeatures of the metal/ceramic beam focussing and directing tube section.

FIG. 17b is a plan view of a dynode ring showing the details of itsstructure.

FIG. 17c is an enlarged detailed view of a portion of the structureshown in FIG. 17b.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Window Configurations andCooling

Window materials useful in this invention include but are not limited toaluminum, titanium, beryllium and other materials such as organicpolymers or polymer composites, such as metal coated polymers, forexample.

FIG. 1 illustrates an improved transmission window assemblyconfiguration which reduces the value of the transverse stress in thewindow foil material to a much lower level by reducing the radius ofcurvature over that of a nominally fiat window configuration.

In FIG. 1 a particle beam accelerator 10 is provided for irradiating aworkpiece, such as a continuous strand or filament 11a. Alternatively, aworkpiece sheet moving transversely with respect to the window openingalong a direction of movement locus marked by the arrow 11b may also beirradiated by the accelerator 10 (see FIG. 4A discussed hereinafter).

The accelerator 10 includes a housing 12 which provides an enclosuredefining an vacuum chamber 21. A particle beam 13 is emitted from asource 15 within the housing 10 and is denoted by the downwardlydirected arrows in FIG. 1. The particle beam 13 may be focused anddirected toward a thin titanium foil window 14 by any suitableconventional beam directing means (not shown). Thus, the particle beam13 from the accelerator 10 may be linearly collimated and directed inconventional fashion, as shown in FIGS. 1, 2 and 4A, or it may be aswept and converged particle ribbon beam from an accelerator 10, inaccordance with the teachings of the referenced and incorporatedcopending patent application Ser. No. 07/569,329, now U.S. Pat. No.5,051,600 and as shown in FIG. 4.

The foil window 14 is formed into an elongated, generally U-shapedchannel structure having a radius of curvature R of the channel portionwhich radius is preferably much smaller than previously existing inconventional fiat window configurations of the prior art in which anyradius of curvature resulted from imposition of a pressure differentialbetween the ambient air outside the window and the vacuum inside thewindow once the window was installed in the accelerator. The foil window14 may be a preform, as depicted in FIGS. 2 and 3 and discussedhereinafter, or it may be formed by following contour-forming peripheralsurfaces of a window mounting structure.

In one presently preferred form shown in FIG. 1, the foil window 14 ismounted between an upper flange structure 16 connected to or forming apart of the housing 12 and a detachable lower flange structure 18. Apolymeric or metal O-ring gasket 20 provides a suitable vacuum sealbetween the foil window 14 and facing surfaces of the upper flange 16. Acontinuous loop of wire having a diameter of approximately 10 mils andformed of a suitable metal, such as tin, is presently preferred forproviding a durable O-ring gasket 20.

A series of screws 22 pass through openings 24 in the lower flange andengage threaded holes 26 formed in the upper flange 16 in order tosecurely affix and seal the window 14 to the housing 10. The flanges 16and 18 and associated structural elements described hereinabove may beformed as an assembly for retrofitting a conventional particle beamaccelerator in order to achieve the advantages realized by practice ofthe principles of the present invention. Alternatively, the flanges 16and 18 may be parts of a particle accelerator, such as the accelerator10, which is specially designed to make practical and effective use ofthe present invention.

The arrangement illustrated in FIG. 1 enables ready and efficientreplacement of the transmission window 14 and provides access to theinterior vacuum chamber 21 defined by the housing 12. Contour-formingperipheral surfaces of the upper and lower flanges 16 and 18 of thisarrangement guide and direct the transmission window 14 into anelongated, curved window structure, which, for the same materialthickness, is considerably stronger than the substantially flattransmission window structures employed in the prior art.

For example, for a three inch wide window using conventional flatflanges in lieu of the flanges 16 and 18, the radius of curvature Rafter vacuum loading would typically have a dimension of about sixinches. Under those same conditions, a three inch wide window 14, whengiven a radius of curvature R of one and one half inches, manifestssignificantly reduced material stress in the thin foil of the window,the stress being less than about one quarter the comparable stresspresent in the vacuum loaded fiat window configuration.

FIG. 2 illustrates a transmission window embodiment 14A of the presentinvention which presents a curved convex surface to the vacuum chamberalong a substantial part of its length. The window 14A may be formedthusly by the configuration of the surfaces of the upper and lowerflanges abutting thereto or it may be preformed to conform closely withthe abutting surfaces of the upper and lower flanges. A preferred way ofmaking the window mounting flanges, when used to conform the window intothe desired curved shape is by electrodynamic machining (EDM).

FIG. 3 illustrates a transmission window embodiment 14B of the presentinvention which presents a preformed curved convex surface to the vacuumchamber and which may be mounted between substantially fiat surfaces ofthe upper and lower window flanges. In all of the embodiments of thisinvention the window 14 may be preshaped to be thinner in those regionsthrough which the particle beam passes and thicker in those regionsadjacent to the window securing structure. In the particular embodimentof the invention shown in FIG. 3, thinning of those regions of thewindow through which the particle beam passes is an advantageous resultof certain methods of preshaping, such as drawing down over a formingsurface, or forming with pressure, vacuum, or intense magnetic field,for examples.

With the new transmission window configuration illustrated in FIG. 1, itis therefore practical to reduce the thickness of the window by one halfand thereby reduce heat dissipation of the window by at least one halfover that of the conventional fiat window configuration. An additionalvery significant advantage is a substantial reduction (about 50% in thisexample) in angularity of scattering of the electrons as they traversethe window. Accelerator power may thereupon be increased to double themaximum value permitted by use of a conventional fiat window and stillretain an additional fifty percent safety margin in window strength.

Significant improvements in window cooling efficiency may also berealized, since forced cooling fluid (gas, mist or liquid) may now bedirected specifically along the surface of the curved window 14 flowingagainst and guided by the curvature. As shown in FIG. 4, a knife-bladeedge nozzle arrangement 28 is formed in the lower flange 18 along oneedge of the curved window 14 and directs cooling fluid flow 29 from apassage 30 directly against the ambient air side of the window 14 alongits entire area in a direction transverse to the longitudinal axis alongwhich the product strand 11a moves, as denoted by the arrows drawnadjacent to the window 14 in FIG. 4. (As also shown in FIG. 4, insideedges 17 of the upper flange structure 16 may be slightly curved toprovide a forming surface for curving the window 14, as desired.) Inthis embodiment, the sheet of cooling fluid should enter the processingchamber tangential to the surface of curvature of the window 14 at theregion of entry. If the sheet is formed and directed too shallowly awayfrom the window, there will be dead air space adjacent to the window 14.If the sheet is formed and directed too steeply toward the window,excessive turbulence of the cooling fluid results.

A fluid cooled base beam-absorption structure 33 having deep cavities 35is provided below the strand 11a to absorb any stray remnants of thebeam 13A emitted in the swept and converged ribbon beam generator 10'.

The structures 10' and 10 shown in FIGS. 4 and 4A manifest an improvedangle of incidence for, and radial acceleration of, the cooling fluidstream 29 relative to the window 14 which has a beneficial effect ofreducing the boundary layer (Which had been a limiting factor in coolingefficiency in prior art fiat window configurations). Improved cooling ofthe transmission window enables use of even higher accelerator powerlevels, since the radiation flux and hence the window power loading maybe increased with increased cooling efficiency.

FIG. 4A shows a more structurally detailed view of a preferredarrangement for directing the cooling stream 29 against the window 14 inthe accelerator 10, as applied in a process for irradiating a sheetworkpiece 11b moving in a direction relative to the window 14 asdepicted in the FIG. 1 diagrammatic view.

Windows 14 of the configuration shown in FIGS. 4, 4A, 5, 6 and 7 arebest cooled by causing high velocity cooling fluid (e.g. air) to flowover the surface thereof in a direction which is transverse to the axialdirection of product strand flow. In this manner, the short air coolingpath and radius yield maximum air velocity while minimizing dispersionand volume flow. When this cooling method is practiced within thestructure depicted in FIGS. 4-7, the cooling air has a minimal effectupon the temperature of the product strand passing through the windowvolume (irradiation zone) along the radial axis of the curved window 14,as best shown in FIG. 5.

The cooling air stream 29 may transport a liquid agent, such as a watermist to the outside surface of the window 14, so that the cooling liquidevaporates in proximity of the window, thereby absorbing the heat ofvaporization to achieve additional heat transfer and cooling of theheated window.

Evaporation of the cooling liquid at the window surface also results ina volume expansion of cooling gas and resulting turbulence which breaksup surface boundary layers which may otherwise form and inhibit coolingefficiency. A nozzle arrangement 28 as shown in FIG. 5 may be employedto inject water or other liquid, solid or particulate material to beprocessed by exposure to the particle beam, onto the airstream in theairflow path 30 and thereby be carried into direct proximity of thesurface of the window 14.

Alternatively, droplets of a fluid material may be sprayed on to thewindow by a suitable nozzle structure. In this alternative approach, thenozzle structure causes a "cloudburst" of material as fine droplets anddirects this mist against the transmission window. This sprayingtechnique would also increase the load bearing capacity of a prior artfiat transmission window.

Further advantages may be obtained by reduction in the particle beamdimensions and by reducing the radius of curvature of the window 14. Infact, a preferred species of the present invention is a tubular windowas depicted in FIG. 8 and discussed hereinafter. These advantages areparticularly evident in realizing efficient yet smaller sized, lowerprime cost particle beam accelerators.

For electron energies over 150 KeV the energy losses of the electronbeam in the window 14 are reduced, for example, by about 19,000 electronvolts for each 0.001 inch reduction in thickness of a titanium alloywindow, wherein titanium is alloyed with vanadium and aluminum. Thissaving is particularly useful in lower energy accelerators, such asthose operating in a range between about 100 and 500 KeV where theenergy loss within the window is most significant.

With reference now to FIG. 5, a modification of the FIG. 1 accelerator10 is shown which advantageously promotes self-centering of the strand11 relative to the window 14, thereby optimally positioning the strand11 in the path of the particle beam for maximum exposure to the beam. Inthis modified accelerator 10', a region 37 of a modified lower flange 18defines a longitudinal well or chamber 32 which oppositely faces thewindow 14. This channel-shaped space 32 enables the laminar airflowsheet, depicted by arrows and identified by the reference numeral 34 toform into a spiral which surrounds the strand 11 and which creates a lowpressure area at the nominal axis of the strand 11 and a surroundinghigh pressure area. This flow arrangement for the cooling stream 34thereby not only effectively draws heat off of and away from the curvedtransmission window 14, it also promotes centering and proper axialalignment of the workpiece 11.

The structural concept depicted in FIG. 5 is extended and presented ingreater detail in FIGS. 6 and 7. Therein, the base structure 18 isprovided with a nitrogen or air flowpath 30, and also with a pluralityof water flow passages 36. The space 32 is defined by a box structure 38which is surrounded by the water flow passages 36, so that the boxstructure 38 will be effectively cooled by flow of water or othersuitable coolant liquid through the flow passages.

With reference to FIG. 8 a transmission window has been formed as acylindrical tube, as by laser welding along a seam line (not shown). Theproduct workpiece, such as the strand 11, is drawn through the insidespace of the tube, while irradiation from the particle beam, denoted bythe arrows 13 is directed from an evacuated chamber side of the particlebeam accelerator, through the thin tubular window 14' and to the strand11.

FIG. 9 shows a mounting arrangement for mounting the tubular window 14'between two flanges 50 and 52 which position and secure the tubularwindow 14' at opposite end regions thereof. Two threaded nuts 54 and 56compress respectively against the flanges 50 and 52, thereby to lock thetube window 14' in place. The flanges 50 and 52 are respectively mountedthrough aligned openings formed in two sidewalls 58 and 60 of a particlebeam accelerator 62. The particle beam accelerator 62 generates anddirects particle beams 13 from one or more emitters toward the window14'. An interior space 64 within the particle beam accelerator 62 ishighly evacuated, whereas the "interior" space defined by the windowtube 14' is exposed to the ambient environment. One can appreciate byinspection of FIGS. 8 and 9 that the tube geometry of the window 14'provides vastly reduced hoop stress across the severe pressure gradientfrom ambient air pressure to the highly evacuated interior space 64.

Cooling of the tube window 14' is an important consideration for itssuccess and practicality. Generally speaking, airflow induced underpressure may be applied to the interior of the tube 14' and conduct awaythe heat generated as the particle beam passes through the thin windowmaterial. Also, in this example a cooling liquid, such as a water mist,may be injected at the periphery of, and carried by, the pressurizedairflow to the window surface, thereby to provide additional cooling tothe window by virtue of the heat of vaporization. Also, the expansion ofvolume resulting from evaporation of the moisture droplets aids inbreaking up surface boundary layers of gas at the window, therebypromoting more intimate contact of the airflow with the window surfaceto be cooled.

FIG. 10 illustrates an improved cooling arrangement employing a coaxialair nozzle structure 66 within a modified threaded nut 54'. The coaxialair nozzle structure 66 is disposed within an annular passage 68 definedin the modified nut 54'. The passageway 68 communicates with a nipple 70for attachment to a supply of cooling air, typically under a pressure of30 to 80 pounds per square inch. The coaxial air nozzle structureprovides a concentric nozzle annulus throughout its inner annularperiphery which is directed toward the inside surface of the tubularwindow 14'. This nozzle creates an annular, layered airflow which passesagainst the tubular window 14 at high velocity. Due to a venturi effectexperienced .within the interior of the tube window 14', some air volumeflow amplification occurs. Because of this amplification, a low pressureregion exists in the throat of the window interior which self centersthe strand 11 and facilitates initially feeding the strand end into andthrough the window (so long as the direction of feed is the same as thedirection of laminar air flow).

The tubular window 14' illustrated in FIGS. 8-10 is particularly usefulwithin the apparatus described in the referenced commonly assigned U.S.Pat. No. 5,051,600.

Radiation Processing of Window Cooling Material

For the processing of materials, such as the irradiation of an aqueoussolution with toxic solutes for the purpose of reduction of the toxicmaterials to less toxic or non-toxic forms, the window cooling air maycarry or be in part or entirely replaced with a fluid stream orcloudburst of mist carrying material to be processed by exposure to theenergetic particle beam. Thus, if it is desired to facilitate aradiation initiated reaction between two separate phases such as aliquid and a gas, the liquid may be sprayed or injected into the gasstream impinging on the window (for example, in the manner shown in FIG.5) or a fluid stream with bubbles of the gas dispersed therein may bedirected against the window. The liquid may also be sprayed directlyonto the window as fine droplets in an atmosphere of the gaseouscoreactant. While a liquid medium is presently most preferred as acarrier medium for carrying (or comprising) the material to beprocessed, it is clear that particulates and other materials to beprocessed may be injected into a fluid stream provided for cooling thetransmission window.

The dimensions of the exit nozzle arrangement, i.e. cooling fluid nozzleopening 28 of FIG. 5 or coaxial air nozzle structure 66 of FIG. 10, canbe spaced so as to establish that the maximum stream thickness flowingover the window is appropriate for the penetration depth of theenergetic particle beam.

Beam window cooling carried out with a liquid component is much moreeffective than air cooling and therefore permits much higher beam fluxthrough the window. With a very high power beam, processing of verylarge amounts of material within a liquid medium or carrier may beachieved economically with a relatively low particle energy. Also, byemploying a thin sheet of liquid-carried material to draw heat away fromthe transmission window, a thicker window may be employed. For example,a window formed of 4 mil thick foil may be advantageously employed inthe liquid materials process. While about 20 kilovolts per mil is lostto heating in the window foil, this heat is advantageously transferredto the liquid material to be processed. At the same time, a more durabletransmission window structure is realized by virtue of the increasedthickness of the window material. Since liquid has a much greater heatcapacity, and since the window is being cooled by the liquid, ratherthan by airflow, a partial vacuum may be pulled across the liquid sideof the window which further reduces stresses in the window foil and addsrobustness and longevity to the window and greater economy to theoverall liquid process. Thus, as the heat capacity of the cooling fluidincreases, the useful thickness of the thin window foil may likewise beincreased.

Turning now to FIG. 11, a liquid materials processing particle beamsystem 100 includes a housing 101 enclosing a particle beam emitter foremitting a particle beam 102 from a source (not shown in this figure).For liquids processing the beam 102 most preferably may be deflected;and, it may also be deflected and converged in accordance with theteachings of the referenced and incorporated, and commonly assigned,co-pending U.S. patent application Ser. No. 07/569,329 filed on Aug. 17,1990, now U.S. Pat. 5,051,600.

Alternatively, the beam 102 may be conventionally formed, focused,accelerated and deflected without convergence. In any event, the beam102 is directed toward and through a curved transmission window 104 ofthe type previously described herein. While a curved transmission window104 is presently most preferred, it will be clearly understood by thoseskilled in the art, that more conventional window structures, such asthe slightly pillowed, nominally flat thin foil transmission windows ofthe prior art, may also be employed with considerably increased efficacywithin the system 100. If there is a vacuum on both sides of the window,then the window can be fiat.

A liquid manifold 106 provides a supply of liquid 108 to be processedunder suitable pressure. The liquid 108 from the liquid manifold 106flows along one or more internal passageways 110 toward a knife-bladeedge structure 112 at one longitudinal periphery of the curvedtransmission window 104. The knife-blade edge structure 112 forms anddirects the liquid 108 against the outside of the transmission window104, thereby coming into contact with it and drawing off the heatgenerated by passage of particles, such as electrons, therethrough. Atthe same time, the beams particles efficaciously pass into and processthe liquid emanating from the knife-blade structure 110, thereby heatingthe liquid to a suitable process temperature and inducing other desiredchanges, either chemical, as with petroleum cracking or chemicalreduction of toxic compounds, or e.g. polymerization of other liquidmaterials, etc.

After passing across the outer surface of the transmission window 104for heat transfer therefrom and for processing, the liquid 108 falls asa stream or expanding sheet into a collection vessel 114 defining aninterior collection space 116. The vessel 114 may advantageously beincluded within, or form a part of, the system housing 101. An outflow118 draws the processed and heated liquid 108 out of the collectionvessel 114, either for transfer or collection at a liquid receiver (notshown) or for heat exchange and recirculation to the inlet manifold 106,as may be desired by a particular process.

The interior space 116 may be evacuated in order to reduce the pressuredifferential or-gradient across the thin foil transmission window 104.By reducing the pressure within the collection vessel space 116 to e.g.about 5 pounds per square inch, or less, the stresses across the window104 are correspondingly reduced, and the window may be operated at ahigher temperature, e.g. 350 degrees C., or higher. Particular choicesof window materials and dimensions including thickness will depend ontemperature, pressure differential, flow rates, heat capacity,viscosity, corrosiveness and other factors of the selected coolingfluid.

As shown in FIG. 12, the knife blade liquid sheet nozzle structure 112may be positionably secured to an interior shelf 113 within the housing101. Screws 115 may be provided to enable positional adjustment of themoveable knife blade structure 112 along a generally horizontal locusdenoted by the double arrow locus line 117. When the blade assembly 112is moved to the left in FIG. 12, the nozzle sheet orifice becomessmaller, and the liquid sheet directed at the thin titanium foil window104 itself becomes correspondingly thinner. Adjustment of the nozzlestructure 112 to the right widens the nozzle orifice and thickens thesheet of process liquid being directed against the curved exteriorsurface of the window 104. Also to be noted in FIG. 12 are the bullnoseupper flange 105 and lower securement flange 107 which secure the e.g.titanium foil window 104 to the housing 101.

Yet another liquid irradiation and processing system 120 is illustrateddiagrammatically in FIG. 13. The system 120 takes advantage of theelevation of the temperature of the irradiated liquid material in such away that a high energy efficiency may be attained. The system 120includes a housing 122 having insulated sidewalls and a particle beamgenerator 123 which emits an energy beam 102 toward and through a thinfoil transmission window 126, most preferably of the curvedconfiguration discussed hereinabove, but which less preferably may be aconventional fiat surface transmission window.

A collection cavity 128 within the housing 122 collects a liquid 130undergoing processing within the system 120. Gases and vapors collectingin the cavity 128 above the level of the liquid 130 are conducted via apipe 132 to a low temperature vapor condenser 134. The vapor condenser134 includes a coolant inlet 151 and a coolant outflow 153 whichconducts coolant to and from the interior space of the condenser 134 inorder to provide desired cooling of the vapors and consequentcondensation thereof.

A vacuum pump 136 is provided in series with the cavity 128, pipe 132and vapor condenser 134 so that the cavity 128 is evacuated. Condensedvapors are either passed out of the system 120 via a valve 138 to anexit conduit 140, or the condensate may be returned as a viscosityreducer to a main fluid stream via a valve 142 and pipe 143 whichcommunicates with a process outflow conduit 144 and flowpath.Advantageously, the process of evacuating the vapor portion of thecavity 128 removes e.g. oxygen and other reactive gases and vapors fromthe process thereby preventing such gases from interfering with thedesired process result. As noted above, a still further significantadvantage of evacuating the cavity 128 is that the reduction in pressureto about 5 psia or less, for example, advantageously reduces the axialand transverse .stresses otherwise present at the transmission window126. These lower stresses make it possible to operate the process atvery high window temperatures, such as 350 degrees C., or higher,without rupture of the thermally weakened thin foil of the window. Notshown in FIG. 13 are other temperature heating/cooling controls andstructure which may be required or included for regulating thetemperatures of certain liquid process materials, depending-on theparticular materials and the desired process temperatures.

A process inlet 146 enables unprocessed liquid, such as highly viscouscrude oil, to enter a thermally graded heat exchanger section 143 of thehousing 122. A series of thermally insulative flow baffle plates 147separate the interior of the section 143 into a series of thermal stagesor levels. At the same time, an internal conduit 150 snakes around thebaffle plates 147 as shown in FIG. 13.

Fluids such as heavy crude oils may have very high viscosities. Toaccommodate high viscosity of the process liquid material, the conduit150 is preferably divided into a series of progressively smallerdiameter sections, with the largest diameter section 150a being locatedat a lowermost, and coolest level within the graded heat exchanger 143.The temperature at the coolest level may be about 28 to 30 degrees C.,for example.

A next smaller diameter section 150b of the conduit 150 sinuously snakesthrough a middle, medium temperature portion of the heat exchanger 143where the temperatures may range from about 100 to 300 degrees C., forexample; while a smallest diameter section 146c extends through anuppermost, hottest portion of the graded heat exchanger 143 havingtemperatures ranging from 300 to 500 degrees C. After leaving theuppermost level, the segment 150c communicates with a knife-blade nozzlestructure 148 of the type discussed e.g. in conjunction with FIGS. 11and 12, for example. In this manner the driving pressure for driving theliquid process material through the conduit 150 may be minimized bytaking advantage of progressive reduction in hydraulic resistance withincreasing temperature of the material.

In applications of liquid irradiation and processing systems of theinvention especially those involving exposure of the window tochemically hostile conditions, for example, high temperature liquids orcorrosive fluids, it is especially advantageous to coat that side of thewindow in contact with the liquid or fluid to be processed with achemically inert or anticorrosion heat resistant coating. Such coatingsinclude thin layers of inert metals such as gold and the noble metals,nickel and the like; and abrasion resistant ceramic and or other oxidelayers, for example, anodized surface coats and the like.

A self contained, transportable fluid process beam system 160 isillustrated in FIG. 14. Therein, a conventional tractor 162 andsemi-trailer contain a system liquid processor 164, power supply 166 andoperator console 168. The diesel engine of the tractor 162 may be usedto power a generator to supply primary operating power for the powersupply 166, or a separate generator may be provided. Hoses 170 and 172respectively provide an inlet and outlet for material to be processedand its carrier fluid medium.

The transportable system 160 may be made to be very rugged, and safe,with necessary radiation shielding, and it may also be made to be usedwithout direct human operator supervision and control. The system 160may thus be taken to and used in oil fields for crude oil viscosityreduction and local cracking to produce refined products for field use.It may be used to lower the hydraulic horsepower required for pumpingthrough pipelines. It may be taken to and advantageously employed toreduce or eliminate toxic contaminants in waste streams or in potablewater supplies.

In this embodiment of the invention, the particle accelerator ispreferably an electron accelerator and the electron emitter ispreferably an elongated electron beam emitter. The particle acceleratorpreferably comprises an all inorganic ion beam focussing and directingstructure, for example, one formed from metal and ceramic components.Thus, the particle beam focussing and directing structure is preferablyan all inorganic structure, for example, a metal and ceramic ionacceleration tube assembly comprising tube sections formed of ceramicand metal, for example, alumina ceramic and titanium componentsconventionally bonded together by heat, pressure and suitable fluxes,and containing internal electrodes. These sections may be boltedtogether using metal gasket seals (for example, aluminum, copper, or tinwire seals) between the component sections. A particular advantage ofsuch structures is that, should a catastrophic condition occur, such asa beam window implosion, the tube assembly can be disassembled quicklyand the components cleaned and baked at a high temperature, that is upto 200° C., without harm to the components. Preferably the internalelectrodes are demountable to facilitate cleaning of the components andelectrodes. An especially preferred acceleration tube assembly is oneintended for ion acceleration and is manufactured by NationalElectrostatics Corporation.

FIG. 15 graphs fluid flow rate as a function of beam power for anelectron beam liquids processor of fixed window area and employing thefluid flow to cool the particle beam window in accordance with theprinciples of the present invention. In the FIG. 15 graph, the electronbeam operated in a KeV range of 150-400, and the liquid knife gap variedfrom about 0.005" to 0.040". Beam scan width varied from about 2 inchesto 10 inches.

FIG. 16 depicts a preferred accelerator unit section, which acts as abeam focussing and directing unit. The accelerator unit 200 includes anupper flange 201 which mates to the filament flange 202 and a lowerflange 203 which mounts to an upper flange of an extension tube (notshown) or to a further accelerator tube section. A series of e.g. 18annular metal dynode rings 204, fused into an assembly with ceramic tubeseparators 205 (shown in greater detail in the enlarged view FIG. 17a)are positioned between the flanges 201 and 203 in vacuum sealingrelation therewith. Each dynode ring 204 includes an inner annular capportion 206. The box shaped focus element 207 is optional, is positionedonly within the accelerator unit section nearest to the filament flange,and is attached to a selected one of the dynode rings in order to be atits potential relative to the negative high voltage and chassis ground.In a preferred embodiment the interior annular cup shaped portion ofeach dynode is secured to the outer portion thereof by suitablemechanical interlocking fasteners and may be readily detached therefrom(e.g. for cleaning) and removed from the accelerator unit section.

The voltage divider network 208 is formed of a series of high volume (10megohm, 2 watt carbon composition) resistors which are spiralled aroundthe dynode rings 204. Some of the resistors of the network 208 areintentionally omitted in FIG. 16 for clarity. The rings 204 have tappoints 209 which provide a predetermined voltage connection from theresistance network 208 to each ring 204. Thus, as the rings 204 extendfrom the top flange 201 to the bottom flange 203, the voltage applied toeach particular ring is dependent upon the tap location and rangesbetween the minus high voltage applied to one or both of the filamentpair and the ground potential of the exit window.

The electron emitter structure 210 includes two holes defined through acentral region of the flange 202 and they receive two electricalfeedthrough insulator fittings 211 and 212 which pass electricalconductors 213 and 214 leading from the secondary of a toroidaltransformer 215 to the emitters (not shown). Preferably the emitterstructure contains two emitters, disposed parallel to each other. Theyare either energized one at a time, the other being used as a spare, orboth are energized at the same time, with the current in one travellingin the opposite direction to that in the other, in order to cancelalternating current components of the filament current source. Inoperation, the beam of electrons 221 is accelerated down the tubeevacuated core and exits towards a transmission window (not shown).

FIG. 17a illustrates a sectional view of a portion of the acceleratorunit section 200. One part of the preferred dynode assembly is aremovable spark gap component 216 installed circumferentially about thefixed portion of the dynode ring 204. The fixed dynode ring is integralto the vacuum envelope and heat bonded to the ceramic tube sections 205.Each adjacent pair of dynode spark gap components comprises a spark gap217 as well as mechanical supports and electrical terminations for theresistor assemblies 208 of FIG. 16.

Another part of the dynode ring 204 is the interior removable cuppedannular section 2 18. The cupped section of adjacent annular pieces nesttogether to eliminate any line of sight paths between the ceramiccomponents 205 and the centrally located beam transmission region. Theexclusion of line of sight paths is necessary to reduce or eliminate thepossibility that charged particles from the beam transmission regioncould migrate out of the central region of the tube and settle upon theinsulating surfaces of the ceramic dynode ring separators eventuallycausing voltage breakdown to occur across the insulator.

FIG. 17b is a plane view of a cupped annular section and fixed portionof a dynode ring further illustrating the interlocking relationshipstherebetween. FIG. 17c shows the details of the interlock design. Thecupped annular section can be removed by rotating the interior of theannulus slightly to align the tabs 219 with a plurality of indents 220in the fixed portion of the dynode ring 204 shown in FIG. 17b and 17c.Thus, the cupped annular sections, resistor assemblies and spark gapcomponents may be readily removed from within the vacuum envelopeassembly and each component may be cleaned as necessary with solvents,followed, if desired, by heating in an oven to restore it substantiallyto its original condition.

EXAMPLE 1 Oil Viscosity Reduction

A screening test was performed with apparatus similar to the FIG. 11apparatus to determine the gross effects of beam dose, dose rate andtemperature upon the viscous characteristics of oil. The samplesirradiated were SAE 120 weight gear oil. Using a control viscosity of100, and measuring viscosities of processed oil with a Brookfieldviscometer using the HB3 spindle and a rotation of 100 RPM, viscosityreductions following radiation processing ranged from 93 to 68, withsome absolute error due to limited quantity of oil. The tests includedwater spray cooling and some under vacuum conditions. At a dose (MRad)of 1.66, the viscosity reduced to 93. When the dose was raised to 15Mrad, the reduced viscosities ranged from 83 to 68. A similar test wasperformed upon Venezuelan Heavy Crude with similar results.

In summary, test results have suggested that reduction of viscosities ofheavy crude oil from this process yields products which are similar tothose expected to result from a more conventional petroleum crackingprocess. Essentially no new compounds were noted as a result of thisprocess.

EXAMPLE 2 Removal of Contaminants from Water

Water containing 0.1 to 0.3% of various textile dyes is irradiated usingthe liquid processor of FIG. 11 a rate of about 1000 gallons an hour andat three minute intervals. Electron beam current is 6 mA at 400 kV. Thecolor of the samples is removed after doses up to 150 kGy.

In similar experiments, water samples containing trace amounts (up to 50micrograms per liter) of methylene chloride, chloroform, carbontetrachloride, 1,1,1-trichloroethane, trichloroethylene andtetrachloroethylene are irradiated to a dose of less than 10 kGy,resulting in essentially complete removal of the contaminants. Similarresults are obtained with bromodichloromethane, dibromochloromethane,bromoform, trans-1,2-dichloroethene, cis-1, 2-dichloroethene,1,1-dichloroethene, 1,2-dichloroethane, 1,1,2, 2-tetrachloroethane,hexachloroethane, hexachloro-1,3-butadiene, vinyl chloride, benzene,toluene, ethylbenzene, o-xylene, m-xylene, pxylene, chlorobenzene,1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, dieldrin,phenol, o-cresol, m-cresol, p-cresol, dieldrin, polychlorinatedbenzenes, polychlorinated biphenyls, dioxins, chlorine containingdioxins, bromine containing dioxins, brominated benzenes, brominatedbiphenyls, aromatic ethers and aromatic polyethers. Thus the processorand the process of the invention can be used to remove toxic orpolluting materials comprising one or more of aliphatic, alkyl-aryl,aryl compounds and organic dyes, each of which independently comprisesone or more hydroxyl, corbonyl, corboxyl, thiol, mercaptan or othersulfur containing moiety, amino, imino, amide, imide, nitro, nitroso orhalogen groups, such as --F, --Cl, --Br and --I, from water or otherliquids such as waste streams.

EXAMPLE 3 Determination of Window Robustness

A test is performed to determine the robustness of a liquid cooledwindow. The window is 0.001 inch thick, homogeneous, and composed of atitanium alloy (3Al 2.5 V), 12 inches wide. The locus of a curve incross section along an active transverse dimension of the active area ofthe window has a radius of curvature of 1.75 inches. The activetransverse dimension of the window is 2.94 inches. The flow rate overthe window is approximately 1000 gph.

To realistically simulate the kind of window power loading expected witha high power beam system, the beam scan is turned off leaving the beamas a spot on the window having approximately 75% of the beam powerconcentrated in an area of 0.75 square inches. The beam is operated forabout 20 minutes beginning with low power and gradually increasing up toa maximum of 5.2 kW (13 mA at 400 kV). This represents a window powerloading of nearly 350 watts/sq. inch. After the test, the window doesshow some minor discoloration in the very highest flux area (probablywell over 500 watts/sq. inch) suggesting that for these liquid flowconditions (mixed turbulent and laminar flows) an upper limit may havebeen approached. For this window, 350 watts/sq. inch corresponds to anenergy dissipation in the window of over 3 kw/gram, which the windowswithstand easily without any sign of mechanical failure. Thus thewindows of this invention can easily handle energy dissipations thereinof 600 watts/gram, for example 750 watts/gram. It is preferred thatwindows of the invention withstand energy dissipations therein of 1000watts/gram, for example 1500 watts/gram. More preferably, windows of theinvention withstand energy dissipations therein of 2000 watts/gram, forexample 2500 watts/gram.

Having thus described an embodiment of the present invention, it willnow be appreciated that the objects of the invention have been fullyachieved, and it will be understood by those skilled in the art thatmany changes in construction and widely differing embodiments andapplications will suggest themselves without departing from the spiritand scope of the invention, as particularly defined by the followingclaims.

What is claimed is:
 1. A transmission window for a particle accelerator,the transmission window being of a thin homogeneous foil having:i) apredetermined thickness, (ii) a predetermined length between a first endand a second end, and (iii) a width when laid flat as a sheet prior toforming, the window:(a) being formed to be mountable on a windowmounting, and (b) along at least part of its length comprising an activearea which is formed to have a locus of a curve in cross section alongan active transverse dimension, such that a radius of curvature R of atleast a portion of the curve in cross section is less than twice thelength of the active transverse dimension.
 2. The transmission windowset forth in claim 1 wherein the radius of curvature R is less than thelength of the active transverse dimension.
 3. The transmission windowset forth in claim 2 wherein the radius of curvature R is not greaterthan approximately one half the length of the active transversedimension.
 4. The transmission window set forth in claim 1 wherein thethin foil is formed into a continuous wall tube geometry.
 5. Thetransmission window set forth in claim 1 wherein the thin foil ispreformed during a manufacturing process to follow said curve along atleast a portion of an active longitudinal dimension, the said portionincluding the active area of the window.
 6. The transmission window setforth in claim 5 wherein the preformed thin foil follows a convexsurface of generally elliptical shape along the active longitudinaldimension of the transmission window.
 7. A transmission window assemblyfor a particle beam accelerator including(i) housing defining a vacuumchamber, (ii) means for generating a particle beam within the vacuumchamber, and (iii) means for directing the particle beam toward aradiation emission end of the housing,the transmission window assemblybeing secured at the radiation emission end of the housing andincluding: (a) plural flange means for defining aligned openings, eachopening having a curve locus in an active transverse dimension lying ina plane substantially perpendicular to a longitudinal dimension of thewindow assembly at the radiation emission end, and (b) a transmissionwindow means for passing the particle beam and being formed of thinhomogeneous foil sheet material of sufficient size after formation toenclose the curve loci of the plural flange means and to extendtherebetween in the said longitudinal dimension and being of apredetermined thickness,the transmission window means being removablymountable between and positioned by the flange means, such that thecurve locus followed by the transmission window means has a radius ofcurvature which does not exceed twice the length of the activetransverse dimension.
 8. The transmission window assembly set forth inclaim 7 further comprising sealing gasket means disposed between thetransmission window means and at least one of the flange means.
 9. Thetransmission window assembly set forth in claim 7 wherein the radius ofcurvature of the window means is not greater than approximately thelength of the active transverse dimension.
 10. The transmission windowassembly set forth in claim 7 wherein the radius of curvature of thewindow is not greater than approximately one half the length of theactive transverse dimension.
 11. The transmission window assembly setforth in claim 7 wherein the transmission window means is formed into atube and mounted in the particle beam accelerator by and between theplural flange means.
 12. The transmission window assembly set forth inclaim 11 further comprising cooling flow directing means for directing aflow of gaseous cooling fluid supplied from a source against the surfaceof the tubular transmission window means.
 13. The transmission windowassembly set forth in claim 12 wherein the cooling flow directing meanscauses the flow of gaseous cooling fluid to be directed longitudinallyadjacently along the tubular transmission window and wherein a productstrand to be irradiated by the particle beam is drawn through thetubular transmission window in the same direction as the flow of gaseouscooling fluid stream.
 14. The transmission window assembly set forth inclaim 13 wherein the flow of gaseous cooling fluid directed along thetubular transmission window means creates a low pressure region in thevicinity of a longitudinal axis along which the product strand is drawn,thereby facilitating alignment and guidance of the strand passingthrough the transmission window means.
 15. The transmission windowassembly set forth in claim 12 further comprising liquid phase materialinjection means for injecting a liquid phase cooling material into theflow of gaseous cooling fluid such that evaporation of the liquid phasematerial promotes further cooling of the tubular transmission windowmeans.
 16. The transmission window assembly set forth in claim 15wherein the preformed transmission window means is preshaped to follow aconvex surface of generally elliptical shape along at least a portion ofthe longitudinal direction.
 17. The transmission window assembly setforth in claim 7 wherein the plural flange means comprise a pair offlanges: an upper flange secured to the emission end of the housing anda removable lower flange, the upper flange .and the lower flangedefining aligned interior openings having a length along thelongitudinal dimension and defining the curve locus along the activetransverse dimension at each end which is followed by the transmissionwindow means.
 18. The transmission window assembly set forth in claim 17further comprising cooling flow directing means for directing a flow ofgaseous cooling fluid supplied from a source against the surface of thetransmission window means.
 19. The transmission window assembly setforth in claim 18 wherein the cooling flow directing means causes theflow of gaseous cooling fluid to be directed as a stream transverselyacross the transmission window means.
 20. The transmission windowassembly set forth in claim 19 wherein the stream directed transverselyacross the transmission window means creates a relatively lower pressureregion in the vicinity of a longitudinal axis along which a productstrand is drawn for irradiation by the particle beam.
 21. Thetransmission window assembly set forth in claim 18 further comprisingcooling liquid injection means for injecting a liquid phase coolingmaterial into the flow of gaseous cooling fluid such that evaporation ofthe liquid phase material promotes further cooling of the transmissionwindow means.
 22. The transmission window assembly set forth in claim 17further comprising liquid coolant passages formed in the lower flangeand a supply of cooling liquid for supplying cooling liquid to theliquid coolant passages.
 23. The transmission window assembly set forthin claim 7 further comprising liquid cooling fluid flow directing meansfor directing a flow of liquid cooling fluid supplied from a sourceagainst the surface of the transmission window means,
 24. Thetransmission window assembly set forth in claim 23 wherein properties ofthe liquid cooling fluid are modified chemically in a predeterminedmanner upon exposure to the particle beam while the cooling fluid iscooling the window means.
 25. The transmission window assembly set forthin claim 7 wherein the cooling flow directing means comprises aknife-blade edge providing structural means positioned adjacent to anedge of the active transverse dimension for directing the cooling fluidas a sheet in substantial alignment with said active transversedimension.
 26. The transmission window assembly set forth in claim 25wherein the knife-blade edge providing structural means is adjustablypositionable in order to control thickness of a liquid sheet of theliquid cooling fluid.
 27. The transmission window assembly set forth inclaim 7 wherein the transmission window means is preformed to follow thesaid curve locus along at least a portion of the longitudinal dimension.28. The transmission window assembly set forth in claim 7, wherein thetransmission window means comprises a radiation emission surface havinga chemically inert anti-corrosion coating.
 29. The transmission windowassembly set forth in claim 28, wherein the chemically inertanti-corrosion coating comprises a chemically inert metal.
 30. Thetransmission window assembly set forth in claim 29, wherein thechemically inert anti-corrosion coating comprises a chemically inertoxide or ceramic.
 31. A particle beam accelerator includinga housingdefining a vacuum chamber, means for generating a particle beam withinthe vacuum chamber, and means for directing the particle beam toward aradiation emission end of the housing,the housing including: (a) pluralflange means,each flange means defining a curve locus in an activetransverse dimension lying in a plane substantially perpendicular to alongitudinal dimension, and (b) a transmission window means for passingthe particle beam, the transmission window means being formed of thinhomogeneous foil sheet material of a size sufficient following formationto enclose the curve locus of the plural flange means and extendingtherebetween in the said longitudinal dimension and being ofpredetermined thickness,the transmission window means being removablymountable between and positioned by the plural flange means, such thatthe curve locus followed by the transmission window means has a radiusof curvature which does not exceed twice the length of the activetransverse dimension.
 32. The particle beam accelerator set forth inclaim 31 further comprising sealing gasket means disposed between thetransmission window means and at least one of the plural flange means.33. The particle beam accelerator set forth in claim 31 wherein theradius of curvature of the window is not greater than approximately thelength of the active transverse dimension.
 34. The particle beamaccelerator set forth in claim 31 wherein the radius of curvature of thewindow means is not greater than approximately one half the length ofthe active transverse dimension.
 35. The particle beam accelerator setforth in claim 31 wherein the transmission window means is formed into atube and mounted in the particle beam accelerator by and positionedbetween the plural flange means.
 36. The particle beam accelerator setforth in claim 35 further comprising cooling flow directing means fordirecting a flow of gaseous cooling fluid supplied from a source againstthe surface of the tubular transmission window means.
 37. The particlebeam accelerator set forth in claim 36 wherein the cooling flowdirecting means causes the flow of gaseous cooling fluid to be directedlongitudinally adjacently along the transmission window means andwherein a product strand to be irradiated by the particle beam is drawnthrough the tubular transmission window in the same direction as theflow of gaseous cooling fluid.
 38. The particle beam accelerator setforth in claim 37 wherein the cooling flow directed along the tubulartransmission window means creates a low pressure region in the vicinityof a longitudinal axis along which the product strand is drawn.
 39. Theparticle beam accelerator set forth in claim 35 further comprisingliquid phase material injection means for injecting a liquid phasecooling material into the flow of gaseous cooling fluid such thatevaporation of the liquid phase material promotes further cooling of thetubular transmission window means.
 40. The particle beam accelerator setforth in claim 35 further comprising cooling flow directing means fordirecting a flow of cooling fluid supplied from a source against thesurface of the tubular transmission window means.
 41. The particle beamaccelerator set forth in claim 40 wherein the cooling flow directingmeans causes the flow of cooling fluid to be directed longitudinallyadjacently along the transmission window means and wherein a productstrand to be irradiated by the particle beam is drawn through thetubular transmission window means in the same direction as the flow ofthe cooling fluid.
 42. The particle beam accelerator set forth in claim31 wherein the plural flange means comprises a pair of flangesincluding: an upper flange at the emission end of the housing, and aremovable lower flange; the upper flange and the lower flange definingaligned interior openings having a length along the longitudinaldimension and defining the curve locus along the active transversedimension at each end followed by the transmission window means.
 43. Theparticle beam accelerator set forth in claim 42 further comprisingcooling flow directing means for directing a flow of gaseous coolingfluid supplied from a source against the surface of the transmissionwindow means.
 44. The particle beam accelerator set forth in claim 43wherein the cooling flow directing means causes the flow of gaseouscooling fluid to be directed transversely across the transmission windowmeans.
 45. The particle beam accelerator set forth in claim 44 whereinthe cooling flow directed transversely across the transmission windowmeans creates a low pressure region in the vicinity of a longitudinalaxis along which a product strand is drawn for irradiation by theparticle beam.
 46. The particle beam accelerator set forth in claim 43further comprising liquid phase material injection means for injecting aliquid phase cooling material into the flow of gaseous cooling fluidsuch that evaporation of the liquid phase material promotes furthercooling of the transmission window means.
 47. The particle beamaccelerator set forth in claim 42 further comprising liquid coolantpassages formed in the lower flange and a supply of cooling liquid forsupplying cooling liquid to the liquid coolant passages.
 48. Theparticle beam accelerator set forth in claim 42 comprising cooling flowdirecting means for directing a flow of cooling fluid supplied from asource against the surface of the transmission window means.
 49. Theparticle beam accelerator set forth in claim 48 wherein the cooling flowdirecting means causes the flow of cooling fluid to be directedtransversely across the transmission window means.
 50. The particle beamaccelerator set forth in claim 49 wherein the cooling flow comprises aliquid supplied from a source which is directed into direct proximityagainst the surface of the transmission window means by the cooling flowdirecting means.
 51. The particle beam accelerator set forth in claim 50wherein the cooling flow directing means comprises a knife-blade edgeproviding structural means positioned adjacent to an edge of the activetransverse dimension.
 52. The particle beam accelerator set forth inclaim 51 wherein the knife-blade edge providing structural means isadjustably positionable in order to control thickness of a liquid sheetof the liquid cooling fluid.
 53. The particle beam accelerator set forthin claim 50 wherein properties of the liquid cooling fluid are modifiedchemically in a predetermined manner upon exposure to the particle beamwhile the liquid cooling fluid is cooling the window means.
 54. Theparticle beam accelerator set forth in claim 31 wherein the transmissionwindow means is preformed to follow the said curve locus along at leasta portion of the longitudinal dimension.
 55. The particle beamaccelerator set forth in claim 47 wherein the preformed transmissionwindow means is preshaped to present a convex surface of generallyelliptical shape to the vacuum chamber.
 56. The particle beamaccelerator set forth in claim 31, wherein the means for directing theparticle beam toward a radiation emission end of the housing comprisesan ion beam focussing and directing structure formed from essentiallyinorganic components.
 57. The particle beam accelerator set forth inclaim 56, wherein the ion beam focussing and directing structure isformed from metal and ceramic components which are bonded together byfusing.
 58. The particle beam accelerator set forth in claim 57, whereinthe ion beam focussing and directing structure is a metal and ceramicion acceleration tube assembly comprising tube sections formed ofceramic and metal bonded together.
 59. The particle beam accelerator setforth in claim 58, wherein the tube sections are formed of aluminaceramic and titanium metal bonded together by heat and pressure.
 60. Theparticle beam accelerator set forth in claim 59, wherein the ionacceleration tube assembly is formed from a plurality of tube sectionscomprising alumina ceramic and titanium metal, bonded together by heatand pressure, the tube sections being attached sequentially together.61. The transmission window assembly set forth in claim 31, wherein thetransmission window means, comprises a radiation emission surface havinga chemically inert anti-corrosion coating.
 62. The transmission windowassembly set forth in claim 61, wherein the chemically inertanti-corrosion coating comprises a chemically inert metal.
 63. Thetransmission window assembly set forth in claim 61, wherein thechemically inert anti-corrosion coating comprises a chemically inertoxide or ceramic.